The present invention relates to electronic module structures, and more particularly to methods for securing covers, electromagnetic shields, and components to circuit substrates.
In many types of electronic modules, it is critical that a cover or electromagnetic shield be placed over a section of electrical components that would typically be mounted on a printed circuit board. To secure covers or electromagnetic shields to circuit substrates, it is conventional to use solder, adhesive, and physical restraints such as fasteners, clamps, pins etc. While these methods have been widely used and have proven to be successful over the years, the use of solder, adhesive and fasteners in some applications are difficult to use, especially in rework or repair situations and in cases where the components being secured are very small. Further, solder requires the use of high temperatures for rework and repairs. Thus, during rework, care has to be taken to avoid disrupting components located near the rework site. Adhesives, on the other hand, may be cured by a variety of means, but generally require heat, solvents or mechanical assistance for rework. Finally, fasteners, clamps and the like are often impractical due to their size.
Therefore, there has been and continues to be a need for a method of automatically assembling electronic modules or components that utilizes a single material and process step to physically secure the components of the module together and which at the same time provides an assembled electronic module that lends itself to rework.
The present invention entails a microelectric module comprising a circuit substrate and at least one cover or electromagnetic shield disposed on the circuit substrate. To secure the cover or electromagnetic shield to the circuit substrate, a heat shrinkable polymer layer or film is extended over the cover or electromagnetic shield and the circuit substrate. The heat shrinkable polymer film or layer, after being heated and shrunk, exerts a downward pressure on the cover or electromagnetic shield, securing the cover or electromagnetic shield to the circuit substrate and at the same time maintaining an electrical contact between the cover or electromagnetic shield and a ground pattern formed on the circuit substrate.
In one embodiment of the present invention, the heat shrinkable polymer film or layer assumes the form of a tubular sleeve. The heat shrinkable polymer tubular sleeve is extended over and around at least one cover or electromagnetic shield and a circuit substrate. Thereafter, the polymer film is subjected to heat causing it to shrink inwardly around the module formed by the cover and circuit substrate. As the polymer film shrinks, this locks the cover or electromagnetic shield in place on the circuit substrate and provides a controlled force that results in continuous electrical contact of the covers or shields against a ground pattern on the circuit substrate.
Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings which are merely illustrative of such invention.